Fuel control means for a model engine

ABSTRACT

Fuel control means for a model engine in which intake air is pre-compressed in a crank chamber of the engine, said fuel control means comprising a pressure responsive fuel control valve provided between a fuel tank and fuel injection nozzle means of the engine, the pressure in the crank chamber being introduced into the valve so as to control its opening in accordance with the crank chamber pressure. The crank chamber pressure is also introduced into the fuel tank so that the fuel in the tank is forced under pressure through the pressure responsive fuel control valve into the engine.

United States Patent 91 Yamda 1 May 22,1973

[54] FUEL CONTROL MEANS FOR A 221 Filed: June 16, 1972 211 App]. No.:263,460

[30] Foreign Application Priority Data Oct. 20, 1971 Japan ..46/96879[52] U.S. Cl ..123/73 A, 123/73 DA, 123/139 AJ, 123/DIG. 3, l23/DIG. 5[51] Int. Cl ..F02b 33/04 [58] Field of Search ..l23/73 A, 73 DA,123/139 AJ, DIG. 5, DIG. 3

[56] References Cited UNITED STATES PATENTS 2,733,694 2/1956 Brebeck..123/DIG. 3

2,722,208 11/1955 Conroy et al ..123/DIG. 5

FOREIGN PATENTS OR APPLICATIONS 747,534 4/1956 Great Britain ..l23/73 APrimary ExaminerAl Lawrence Smith Assistant ExaminerDennis TothAttorney-Karl W. Flocks [57] ABSTRACT Fuel control means for a modelengine in which intake air is pre-compressed in a crank chamber of theengine, said fuel control means comprising a pressure responsive fuelcontrol valve provided between a fuel tank and fuel injection nozzlemeans of the engine, the pressure in the crank chamber being introducedinto the valve so as to control its opening in accordance with the crankchamber pressure. The crank chamber pressure is also introduced into thefuel tank so that the fuel in the tank is forced under pressure throughthe pressure responsive fuel control valve into the engme.

4 Claims, 1 Drawing Figure FUEL CONTROL MEANS FOR A MODEL ENGINE Thepresent invention relates to a model engine, and more particularly to anautomatic fuel control system fora model engine.

In a conventional model engine, supply of fuel to the engine has beencontrolled by a throat or Venturi passage provided in an air intakepassage of the engine for providing a suction pressure therein inaccordance with the amount of air flow in the intake passage so thatfuel is taken under the action of the suction pressure from a fuel tankthrough a suitable conduit and a fuel injection nozzle into the engine.This known arrangement, however, has a lot of disadvantages. Forexample, when a throttle valve in the air intake passage is closed toprovide a low speed operation, the suction pressure in the throatpassage is reduced in correspondence with the decrease in air flowtherein, so that a stable fuel supply cannot be ensured. Further, whenthe throttle valve is rapidly opened, the fuel flow into the enginecannot increase as rapid as the air flow does.

Further, when theengine is mounted on a model plane or a model boat, thefuel tank is always subjected to the influence of centrifugal force orinertia force due to the movement of the model plane or the model boat.Particularly, in case of a model plane which is expected to performmovements in three dimensional directions, the engine is expected totake various attitudes and the position of the fuel tank with respect tothe engine may always chahge. Therefore, the amount of fuel supplycannot be uniform when the fuel is taken into the engine under a suctionpressure.

As an effective solution for increasing the engine output, an increasedamount of fuel-air mixture may be taken into the engine. For thispurpose, it may be conceived to increase the cross-sectional area of theintake Venturi portion and that of the hollow interior of enginecrankshaft which constitutes a portion of the intake passage. However,since the increased crosssectional area of the intake Venturi portionwill correspondingly reduce the suction pressure produced therein, thestable fuel supply cannot be ensured anymore when the cross-sectionalarea of the Venturi portion is excessively increased. Thus, there is apractical limit in increasing the engine output in the conventionalarrangement. l i

The present invention has a primary object to eliminate theaforementioned disadvantages of the conventional model engine.

Another object of the present invention is to provide I a fuel controlmeans for a model engine which can provide a stable fuel supplythroughout the operation range of the engine.

A further object of the present invention is to provide a fuel controlmeans which can provide an increased engine output.

According to the present invention, there is provided a fuel controlmeans for a model engine having a cylinder, a crankcase defining a crankchamber, a piston disposed in said cylinder for reciprocating movement,a crank shaft connected with said piston through a connecting rod, anintake passage which is in communication with the crank chamber, intakeport means communicating with the crank chamber and opening into thecylinder, exhaust port means opening into the cylinder, and fuelinjection nozzle means provided in the intake passage, said fuel controlmeans comprising a pressure responsive fuel control valve providedbetween a fuel tank and said fuel injection nozzle means, and means forintroducing the pressure in the crank chamber of the engine to thepressure responsive fuel control valve so that the opening of the valveis increased in accordance with the increase in the pressure in thecrank chamber.

According to a further aspect of the present invention, said fuel tankis a shielded tank and means is provided for introducing the pressure inthe crank chamber into the fuel tank through non-return valve means sothat the fuel in the tank is forced by the pressure through said controlvalve into the engine.

The pressure responsive fuel control valve may include a pressureresponsive diaphragm which is connected to a valve member forcontrolling the fuel passage into the engine.

These and other objects and features of the present invention willbecome apparent from the following descriptions of a preferredembodiment thereof taking reference to the accompanying drawing which isa diagrammatical view, partially in section of a model engine and itsfuel control means embodying the features of the present invention.

Referring to the drawing, the reference numeral 1 generally designates amodel engine of substantially known type having a cylinder 2 and a crankcase 3 defining a crank chamber 4. Within the cylinder 2, there isdesposed a piston 5 for reciprocating movement therein. The cylinder 2and the piston 5 define a combustion chamber in the cylinder as is wellknown in the art. The reference numeral 6 shows a crank shaft having acrank end connected through a connecting rod 7 with the piston 5. Theother end of the crank shaft 6 has secured thereto a propeller 8 of amodel plane or a model boat. As seen in the drawing, the crank shaft 6passes through a cylindrical bearing portion 9 integrally formed withthe crank case 3 and having an air intake conduit 10 including a throator Venturi portion 11. The crank shaft 6 is formed adjacent to its endconnected to the rod 7 with an axial bore 12 opening to the crankchamber 4. The crank shaft 6 is further formed with a slot 13 connectingthe interior of the axial bore to the exterior of the crank shaft 6. Theposition of the slot 13 is such that during the compression stroke ofthe engine, that is, when the piston 5 is moving up, it is brought intocommunication with the conduit 10 whereby an intake passage to the crankchamber 4 is completed. Further, the engine is also provided withscavenging ports 14 which are opened to the cylinder wall and connectthe crank chamber 4 with the combustion chamber at a suitable timingduring the expansion stroke or downward movement of the piston 5. Theengine is further provided with exhaust ports 15 as is well known in theart. In the conduit 10, there is dis posed a fuel injection nozzle 16and a butterfly type throttle valve 17. The reference numeral 18designates an ignition plug.

The operation of the engine of this type is widely known in the art, sothat the detailed descriptions thereof will be omitted.

According to a feature of the present invention, the cylindrical bearingportion 9 is provided with a pressure take-off port 19 in such aposition that it comes into communication with the slot 13 formed in thecrank shaft 6 at a suitable timing during the downward stroke of thepiston 5. Thus, the pressure in the crank chamber 4 is taken out throughthe slot 13 and the port 19 and introduced into a pressure responsivefuel control valve which is generally designated by the referencenumeral 20 and disposed in a fuel supply line between a fuel tank 21 andthe fuel injection nozzle 16.

The fuel control valve 20 includes a pressure responsive diaphragm 22which divides a chamber in a casing 25 into a pressure chamber 23 and alow pressure chamber 24. The diaphragm 22 is connected with a valvemember 26 which co-operates with a valve seat 27 formed in the fuel flowpassage in the casing 25 so as to control the fuel flow in accordancewith the position of the valve member 26. The pressure in the crankchamber 4 taken out through the slot 13 in the crank shaft 6 and theport 19 is transmitted through a line 27 into the pressure chamber 23 ofthe fuel control valve 20. A spring 28 acting on the valve member 26serves to urge the valve member 26 toward the closed position, while thepressure acting on the diaphragm 22 serves to urge the valve membertoward the open position. The spring is seated on an adjustable plugmember 29 threadably inserted into the casing 25. Thus, the position ofthe valve member 26 is determined by the pressure introduced into thepressure chamber 23 and the adjustment of the plug member 29.

The pressure in the crank chamber 4 is further introduced through theline 27 and a further line 30 into the top space of the fuel tank 21.The reference numeral 31 designates a non-return valve provided at theentrance of the crank chamber pressure into the fuel tank 21. The fuelfrom the tank 21 is introduced through a line 33 into the inlet 34 ofthe fuel line in the casing 25 of the fuel control valve 20. The fuelfrom the outlet 35 of the fuel line in the fuel control valve 20 ispassed through a line 36 into the fuel injection nozzle 16.

Thus, in operation of the engine as described above, the positivepressure in the crank chamber 4 is introduced through the slot 13, theport 19 and the line 27 into the pressure chamber 23 of the fuel controlvalve 20, so that the opening of the valve is controlled in accordancewith the pressure in the crank chamber. Therefore, it is possible toincrease the fuel flow in accordance with the increase in the opening ofthe throttle valve 17. Further, the positive pressure in the crankchamber is also introduced into the fuel tank 21 through the line 30 andthe non-return valve 31. Therefore, the fuel is forced under pressurefrom the tank 21 into the fuel control valve 20 and then into the fuelinjection valve 16. This feature is effective to ensure positive fuelsupply irrespective of the change in attitude of the model plane or themodel boat on which the engine is mounted. Further, according to thefeatures of the present invention, it is possible to increase thecrosssectional area of the throat or Venturi portion without having anyadverse effect on the supply of fuel since the fuel is forced underpressure from the fuel tank to provide a positive fuel flow. Therefore,it is possible to provide an engine of increased output by an air intakepassage of increased cross-sectional area.

Although the invention has been illustrated and described with referenceto a preferred embodiment, it should be noted that the invention is notlimited to the details of the structure but changes and modificationscan be made without departing from the scope of the appended claims. Forexample, the fuel control valve 20 should not necessarily be separatedfrom the engine 1 but can be directly secured to the crank case of theengine if desired.

1 claim:

1. Fuel control means for a model engine including a cylinder, atcrankcase defining a crank chamber, a piston disposed in said cylinderfor reciprocating movement, a crank shaft connected with said pistonthrough a connecting rod, an intake passage which is in communicationwith the crank chamber, and an intake port means communicating with thecrank chamber and opening into the cylinder whereby fuel-air mixture ispassed through the intake passage into the crank chamber to becompressed therein and thereafter through the intake port means into thecylinder, characterized by the fact that said fuel control meanscomprises a pressure responsive fuel control valve provided between afuel tank and fuel injection nozzle means of the engine, and means forintroducing the pressure in the crank chamber of the engine to thepressure responsive fuel control valve so that the opening of the valveis increased in accordance with the increase in the crank chamberpressure.

2. Fuel control means in accordance with claim 1, in which said fueltank is a shielded tank and means is provided for introducing thepressure in the crank chamber into the fuel tank through non-returnvalve means so that the fuel in the tank is forced under pressurethrough said control valve into the engine.

3. Fuel control means in accordance with claim 1 in which said pressureresponsive fuel control valve includes a pressure responsive diaphragmwhich is connected to a valve member for controlling the opening of thevalve in accordance with the crank chamber pressure.

4. Fuel control means in accordance with claim 1 in which said crankshaft is formed with an axial bore opening into the crank chamber and aslot is formed in the crank shaft in such a position that it connectsthe intake passage to the crank chamber at a suitable timing during thecompression stroke of the engine, and said means for introducing thecrank chamber pressure into the fuel control valve includes a portprovided in the engine at such a position that it is brought intocommunication with said slot in the crank shaft at least when positivepressure is produced in the crank chamber.

1. Fuel control means for a model engine including a cylinder, acrankcase defining a crank chamber, a piston disposed in said cylinderfor reciprocating movement, a crank shaft connected with said pistonthrough a connecting rod, an intake passage which is in communicationwith the crank chamber, and an intake port means communicating with thecrank chamber and opening into the cylinder whereby fuel-air mixture ispassed through the intake passage into the crank chamber to becompressed therein and thereafter through the intake port means into thecylinder, characterized by the fact that said fuel control meanscomprises a pressure responsive fuel control valve provided between afuel tank and fuel injection nozzle means of the engine, and means forintroducing the pressure in the crank chamber of the engine to thepressure responsive fuel control valve so that the opening of the valveis increased in accordance with the increase in the crank chamberpressure.
 2. Fuel control means in accordance with claim 1, in whichsaid fuel tank is a shielded tank and means is provided for introducingthe pressure in the crank chamber into the fuel tank through non-returnvalve means so that the fuel in the tank is forced under pressurethrough said control valve into the engine.
 3. Fuel control means inaccordance with claim 1 in which said pressure responsive fuel controlvalve includes a pressure responsive diaphragm which is connected to avalve member for controlling the opening of the valve in accordance withthe crank chamber pressure.
 4. Fuel control means in accordance withclaim 1 in which said crank shaft is formed with an axial bore openinginto the crank chamber and a slot is formed in the crank shaft in such aposition that it connects the intake passage to the crank chamber at asuitable timing during the compression stroke of the engine, and saidmeans for introducing the crank chamber pressure into the fuel controlvalve includes a port provided in the engine at such a position that itis brought into communication with said slot in the crank shaft at leastwhen positive pressure is produced in the crank chamber.